1. Field
The present disclosure relates crossed-field devices using radioactive isotopes. Particularly, this disclosure relates to power generation in crossed-field devices employing radioactive isotopes.
2. Description of the Related Art
Power systems providing electrical power for spacecraft have traditionally utilized solar energy or radioactive materials as a power source. Solar power systems, employing solar cells to capture power from the sun and convert it to electrical energy, are often used in satellite applications where the spacecraft remains within reasonable proximity and view of the sun. Among power systems using radioactive isotopes (radioisotopes) as fuel in space applications, there are two significant types, reactor-based systems and radioisotope thermal generators (RTGs). Although a typical RTG delivers less power than a typical reactor-based system, reactor-based power systems are much more complex and less reliable than RTGs.
A radioisotope thermal generator (RTG) is a solid state electrical device which develops electrical power from a decaying radioisotope. A typical RTG comprises a central core of a decaying radioisotope, such as 238Pu. The radioisotope generates heat as it decays. The RTG converts the heat energy of a decaying radioisotope into electricity through an array of thermocouples. A thermocouple converts thermal energy directly into electrical energy. For example, a thermocouple may be made of two metal materials that can both conduct electricity. They are connected to each other in a closed electrical circuit. If the two metals are at different temperatures, an electric current will flow in the circuit delivering electrical power. Excess heat energy is rejected from the RTG. Due to the use of the radioisotope, the entire RTG must be properly shielded.
Unfortunately, conversion of the heat energy to electricity makes RTGs very inefficient. RTGs operate with an energy conversion efficiency of less than ten percent, typically less than five percent. Most of the energy from the decaying radioisotope is lost as excess thermal energy and must be rejected from the spacecraft. Thus, RTGs waste much of the available energy from the decaying radioisotope. In addition, RTGs are relatively expensive to manufacture (although not as expensive as reactor-based power systems).
In view of the foregoing, there is a need in the art for power systems in space applications that are simple, reliable, safe and less expensive. Further, for power systems which employ radioactive isotopes, there is a need for such power systems to obtain higher energy conversion efficiencies. As detailed hereafter, these and other needs are satisfied by the present disclosure.